GWD27-3 to 6 鸟飞翔的起源理论 欢迎讨论

qianrene

The “cursorial”(running)

(45) hypothesis holds that small

dinosaurs ran along the ground

and stretched out their arms for

balance as they leaped into the

air after insect prey or, perhaps,

(50) to avoid predators.

Q5对应红色部分

C.    A possible reason why bird ancestors might have been engaging in activities that eventually evolved into flight翻译：为什么会参与到飞的活动中

qincong83

宝儿，我们几次都在同一题目发贴哈～呵呵

啥时候考？

阿土莎莎

up

lichabrend

up

cecila

本月题啊 up 一个

mickeychen

晕~~~今天做到这道题，居然是本月KFC。顶一下

第5题有点难啊，我也选错了，不过居然选了D，真是鬼使神差，唉

smilecrystal

Q5：
E：两个理论在黄色部分对应
C：绿色部分只在cursorial理论中提出。

Two
opposing scenarios, the “arboreal” hypothesis and the “cursorial” hypothesis,
have traditionally been put forward concerning the origins of bird flight. The
“arboreal” hypothesis holds that bird ancestors began to fly by climbing trees
and gliding down from branches with the help of incipient feathers: the height
of trees provides a good starting place for launching flight, especially
through gliding. As feathers became larger over
time, flapping flight evolved and birds finally became fully air-borne.
                This
hypothesis makes intuitive sense, but certain aspects are troubling.
Archaeopteryx (the earliest known bird) and its maniraptoran dinosaur cousins
have no obviously arboreal adaptations, such as feet fully adapted for
perching. Perhaps some of them could climb trees, but no convincing analysis
has demonstrated how Archaeopteryx would have both climbed and flown with its forelimbs,
and there were no plants taller than a few meters in the environments where
Archaeopteryx fossils have been found. Even if the animals could climb trees,
this ability is not synonymous with gliding ability. (Many small animals, and
even some goats and kangaroos, are capable of climbing trees but are not
gliders.) Besides, Archaeopteryx shows no obvious features of gliders, such as
a broad membrane connecting forelimbs and hind limbs.

    

  
The “cursorial”(running) hypothesis holds that small dinosaurs ran along
the ground and stretched out their arms for balance as they leaped into the air
after insect prey or, perhaps, to avoid predators. Even
rudimentary feathers on forelimbs could have expanded the arm’s surface area to
enhance lift slightly. Larger feathers could have increased lift incrementally,
until sustained flight was gradually achieved. Of course, a leap into the air
does not provide the acceleration produced by dropping out of a tree; an animal
would have to run quite fast to take off. Still, some small terrestrial animals
can achieve high speeds. The cursorial hypothesis is strengthened by the fact
that the immediate theropod dinosaur ancestors of birds were terrestrial, and
they had the traits needed for high lift off speeds: they were small, agile,
lightly built, long-legged, and good runners. And because
they were bipedal, their arms were free to evolve flapping flight, which cannot
be said for other reptiles of their time.
            

minirainbow

想请问一下

Q 6:

The passage suggests which of the following regarding the climbing ability of Archaeopteryx?

A.     Its ability to climb trees was likely hindered by the presence of incipient feathers on its forelimbs.

B.     It was probably better at climbing trees than were its maniraptoran dinosaur cousins.

C.     It had certain physical adaptations that suggest it was skilled at climbing trees.

D.     Scientists have recently discovered fossil evidence suggesting it could not climb trees.

E.      Scientists are uncertain whether it was capable of climbing trees

该怎么做呢

该怎么做呢

rodmantang

Q6:  A为什么不对？

jonathan1987

edce